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michaeldejong
10-25-2013, 09:43 PM
Hello, I have been doing some experimenting with Radiosity in Lightwave this week and came across something.
In an environment that is completely lit using highly illuminated polygons, the scene takes on a very flat and dull
appearance. For example a simple sphere has no highlights on it in the same way it would if there were a traditional
lightsource shining on it. I have tried various surface settings but keep getting the same type of results.

Any feedback?

michaeldejong
10-25-2013, 11:12 PM
One direction I was heading was trying to figure out a way for a surface to reflect only the 'lights' that I had in the scene but not reflect the surrounding environment. This would create the highlights I am trying to get without making the object look reflective. However I do not know how I would achieve this.

djwaterman
10-26-2013, 12:12 AM
Just put a highly illumintated object somewhere around, above or close to the object you want the highlight on (a highlight or specular hit is really just a reflection of a light source), the surface should have reflectivity enabled and if you want realism it must have some kind of Fresnel working on it too. If it is a non-mirror surface then just make the reflective value very blurry. You wont need specular values at all if you use reflective values, specular only reacts to lights, and you stated you don't have any in your scene.

RebelHill
10-26-2013, 04:20 AM
In reality there's no such thing as specular and reflection... its ALL reflection. Specular suface parameter in CG is just a "cheat" to give the look of highly softened/blurry reflections (without of having to calculate actual reflection blurring). This cheat, however, comes from the light objects themselves, and when using GI, luminous geo, etc... thats not there, so you have to use reflection.... or put some lights around, positioned as you need them... and set their options to affect specular only.

jasonwestmas
10-26-2013, 04:35 AM
I haven't seen your image but keep in mind that a "completely lit" scene/lighting condition literally means that every polygon is lit up evenly on all sides. This will in fact make your surfaces appear to be super flat and non-dimensional. So of course the solution is to unevenly light your subject matter and keeping your lights pointed in opposing directions from where the camera is pointing helps too.

Areyos Alektor
10-28-2013, 03:24 PM
You can show us your scene and your settings of surfaces / lights ?

For the "Specular" there are different options : "Exclude", "Light Probe" (HDR), "Photometric" (IES), "Specular Map". You may need "Falloff", or paint your "Specular" on a baking.

Danner
10-28-2013, 03:35 PM
Area lights or linear lights render much faster if you turn off Affect Diffuse, and only leave Affect Specular on. I often use this trick to simulate specular hightlights that come from light sources like windows that are letting environment light come in or to simulate the specularity from scenes lit by luminous polygons.

shrox
10-28-2013, 03:56 PM
In reality there's no such thing as specular and reflection... its ALL reflection...

I hadn't thought of that. Of course now it's obvious.

grabiller
08-06-2014, 06:03 AM
Hello, I have been doing some experimenting with Radiosity in Lightwave this week and came across something.
In an environment that is completely lit using highly illuminated polygons, the scene takes on a very flat and dull
appearance. For example a simple sphere has no highlights on it in the same way it would if there were a traditional
lightsource shining on it. I have tried various surface settings but keep getting the same type of results.

Any feedback?With GI only driven by illuminated polygons and trying to be physically "plausible", there are time you want to cheat a bit for artistic reasons and decouple the GI intensity from the "specular/reflection" intensity.

You can do this directly from the illuminated material by filtering radiosity rays from direct rays with a logic node:

123522

In the image above, "if true" means we are dealing with a radiosity ray, a luminosity value of 7.8 is given. "if false" - that is not a radiosity ray - then a value of 46.8 is given, "boosting" the specular/reflection intensity of the illuminated polygon.

Doing so though, direct visibility of your illuminated polygons will also be washed out (white) which may be a problem if you use textured illuminated polygons.

In this case you can add a bounce filter:

123523

In the image above, the Logic(2) "if true" luminosity value will be used for specular/reflection and the "if false" for direct view of the illuminated polygons.

This way you can separately adjust the intensity of radiosity, specular/reflection and direct intensity of your illuminated polygons.

Hope this helps.

Cheers,
Guy.

Pensart
01-07-2015, 02:42 PM
Wow Guy, that's an amazing tip! Works great. Do you have a tip to soften those highlights. Like the glossiness works on specularity.
And maybe another tip where we could learn more about ray's and bounces?

Cheers,
GP.